Means of reinforcing concrete



Jan. 2, 1940. R g KENNEDY 2,185,749

MEANS OF REINFORCING CONCRETE Filed Jan. 29, 1937 INVENTOR Patented Jan.2, 1940 UNITED STATES PATENTgOFFICE:If

1 3- i Q .1 2,185,749 v MEANS OF nnmroncmc coNcnE'm Robert CharlesKennedy, Oakland, Calif. Application January 29, 1937, Serial No.123,001

1 Claim. (01. 72-71) on the rods is for, the purpose of decreasingtheThis invention relates to a method of combining metal and concrete toform the walls of pressure vessels such as tanks and pipes, or other Iconcrete structures, in such manner as to prevent 5 cracks developing inthe concrete and to fully utilize the strength of the metal.

It-is common experience in building concrete vessels reinforced withsteel rods simply embedded g in the concrete, that the concrete, beinglow in tensile strength, will develop cracks before the jsteel hasassumed its proper working stress. 3 Such cracks also result from thenatural tendency of concrete to shrink as it sets. Such tendency, beingresisted by the rigid steel bars, causes racks to develop. Cracks resultin leakage, and {the weakening of the concrete wall for takingo'mpressive and shearing stresses which it may ,also at times berequired to withstand. Other esults are corrosion of the steel bars andprogres- 't-sive disintegration of the concrete.

A method has heretofore been utilized for prew the cracking of concretepressure vessels y fineans of steel bands equipped with turnbuckles,placed around the previously constructed con'erete walls and tightenedto such degree by :'means' of the turnbuckles that the concrete is'g'placed in compression. By adjusting the stress inthe steel andconcrete to proper degree in this manner before pressure is placed inthe vessel, it possible to prevent any tension in the concrete hriiunderpressure, and thereby cracks are iavoided. However, since it isnoteconomically easible to construct the concrete walls to a per-;jT-fectly cylindrical shape, the rods tend to bear 35 ong solatedpoints around the circumference instead of securing uniform bearingthroughout their length. As a result, a crushing of the concrete takesplace at these high points. Also with thisfmethod, advantage cannot betaken of the A0 economy high-strength steels, since higher qstressedrods would out still deeper into the con crete. In order to provide theadditional bearingfrequired even for ordinary soft steels, it hascustomary to apply a layer of concrete out- 45 side jof the steel rods,somepart of which flows into the spaces between the rods and theconcrete.

The. additional concrete layer also protects the rods from corrosion andprovides architectural advantages.

50 second method for overcoming the cracldng of greinforced concretepressure vesselsis to coat the' adjustable rods with asphalt or otherplastic material and then pour the entire thickness of concrete wall atone time, except for recesses for 56 operating the turnbuckles. Theplastic coating bond with the concrete, so that the rods can betightened withthe turnbuckles. One difllculty with this method is thatit is not possible to sumciently prevent bonding between the steel rodsand the concrete by such plastic coatings as to permit of uniformstressing of the rods, unless the turnbuckles are placed at such shortintervals as to be uneconomical. Another difliculty is that the economyof the higher strength steels cannot be secured, due to greater tendencyof the smaller bars to cut through the plastic material along the curveand thus still further increase frictional resistance to propertightening.

The purpose of my invention is to overcome the above mentioneddisadvantages of existing types of construction and to provide astructure that will render equal or better service, and at the same timebe less expensive to build.

My invention covers the reinforcing of concrete by means of adjustablemetal rods which have been placed in tubes. of metal or other material,such rods fitting loosely within the tubes so as to permit of freelongitudinal movement of the rods. Grease or other lubricant may beenclosed in the tubes with the rods to facilitate movement and to act asa preservative. The entire thickness of tank wall is poured at one time,leaving recesses at proper intervals for the turnbuckles. After theconcrete has set for the proper period, the rods are tightened by meansof the turnbuckles to a predetermined stress. The recesses may either befilled with concrete after the adjustment is complete or left accessiblefor further adjustment if required.

Referring to Figures 1 and 2, the metal band is marked I. This band ismade up of one or more units, depending upon the size of the structure.,Each unit is provided with threaded ends and coupled to the adjacentunits by means of threaded turnbuckles 2, or is provided with otheradjustable means for tightening. The bands are enclosed in tubes orsheaths 3 in which they are free to slide, except that the portionswithin the recesses are not so enclosed. These tubes may be bent aroundthe rods by drawing the rods through a properly shaped orifice togethwith strips of sheet metal, or by spirally wrap ng the strips around therods or by inserting the rods in tubes previously formed, or by anyother suitable method. A lubricant may be added either during or afterthe placing of the tubes around the rods. The rods and tubes are thenbent to the required curve and secured in place by a suitable means, andthe concrete forms are erected in the usual manner, but withprovisionfor forming recesses 4 at the turnbuckles. The distance betweenrecesses should preferably be one-half the length of the rod units, asshown in g Figure 1, so that the turnbuckles may be staggered, and sothat the rods may be vibrated, mechanically or otherwise at pointsmidway between turnbuckles to facilitate movement during tightening. Theconcrete wall I is then poured, 10 to the full thickness and after asuillcient period of time for proper setting, the forms are removed. Theturnbuckles are then tightened to a predetermined stress. The recessesmay be filled with concrete or may be left accessible for 1' futureinspection and adjustment of the turnbuckles.

Advantages of my invention when used for cylindrical vessels such astanks or pipes, are as follows:

a (1) It makes possible the pouring of the full thickness of wall at onetime, and saves the cost of additional concrete or mortar applied afterthe steel rods are adjusted.

(2) The tension in the adjustable rods is made 35 approximately uniformthroughout their length because of the low frictionalresistance tomovement of metal on metal.

(3) It makes possible uniform and adequate bearing for theadjustablerods throughout the a) length thereof.

(4) The saving in material cost through the use of high-strength metalsis made possible because of the ilrm bearing secured between the metaltubes and the adjustable rods.

(5) The concrete wall may be made thinner I because the use of small,high strength rods and turnbuckles is possible.

(6) It makes possible the further adjustment of the rods after thestructure has been in service. 10

A similar method of permitting adjustment of metal reinforcing rods maybe used for tanks or vessels having straight walls, or for beams. All ofthe advantages enumerated herein for cylindrical vessels when my methodof reinforcing is used, apply also tothe latter structures.

I claim as my invention:

Reinforcement for a curved concrete wall, consisting of metal rodsplaced loosely within tubes m encased in the concrete and madecontinuous around the wall by means of adjustable threaded connectionson said rods for placing the same in tension so as to exert a radialpressure on the concrete, said tube enclosures having their ends 25clear of the abutments on the rods so that none of the rod tension willbe absorbed directly by axial compression in the enclosing tubes.

ROBERT CHARLES KENNEDY. so

